The present invention relates in general to a coating apparatus and specifically, to an apparatus and method for simultaneously coating and measuring a part, and simultaneously coating the part based on the desired dimension of the part, desired coating thickness or both the desired dimension and coating thickness.
Several different types of parts that rub, slide rotate or otherwise move are manufactured and assembled for various industries. The parts are used on different types of products, devices, equipment and machines. The characteristics of the parts vary based on the particular use for the parts. Some parts used in certain products, devices, equipment and machines are often subject to stress such as wear and heat. Eventually, certain parts break or become ineffective after continuous and repeated use.
One method commonly used to increase the durability of the parts subject to various types of stresses during operation is to apply protective coatings to the parts. Some coatings protect parts against friction or wear so that the parts are more durable and last longer in operation. Other coatings enhance the aesthetic appearance or corrosion resistance of the parts. Coatings may be applied to the entire part or only applied to a particular wall, portion or section of the part. The particular coating, and application of the coating, depends in part on the part and the coating process requested or desired by the manufacturer of the part, purchaser of the part or user of the part.
Known coating apparatus coat several different types of parts including machined, threaded, fabricated, molded and die-cast parts. Such parts are typically manually placed on a part holder or support and then sprayed with a coating. The part may be moved as necessary to coat the part or the particular portions of the part. The vast majority of parts have dimensional tolerances or tolerance levels, and design specifications that limit the size (including all dimensions) of the part and the amount of coating, such as the maximum and minimum amount of the coating that may be applied to the part or any section, portion or dimension of the part. The maximum and minimum coating thicknesses for a part or parts are determined based on mechanical, dimensional and/or corrosion requirements and other similar quality or design parameters. The dimensional tolerances and design specifications are determined from detailed calculations based on the particular machine, equipment, product, device or industrial operation that the part will be used in. Therefore, the part must be measured to ensure that the part falls within and does not exceed the particular dimension tolerances and/or maximum and minimum coating thicknesses specified for the part so the part will fit to allow assembly of the part and function for the design and/or warranty life of the unit or assembly.
In one known process, non-coated parts are initially measured to determine if they are within an acceptable dimensional range. Some non-coated parts are too large and cannot be coated because the coating will make the parts larger than the upper dimensional limit of the parts, and unfit for use. Other non-coated parts are too small and cannot be coated because too much coating would have to be applied to the parts in order to meet the predetermined dimensional tolerances. Such excessive coating on a part may become weak and may be prone to breaking or causing the part to fail during operation. Such unusable parts are usually discarded or recycled. The non-coated parts that are within an acceptable dimensional range for coating are individually placed on a part support and sprayed or coated by a sprayer. The sprayer sprays or coats the part with an amount of coating determined according to a particular procedure that is calculated, and often estimated, by the operator or processor so that a reasonably sufficient amount of coating is applied to the part to make the part within dimensional tolerances. In certain known coating systems, the amount of coating is not determined for each part, but rather for a group or lot of parts. Therefore, the amount of coating applied to each part may or may not be based on the exact measurement of such part as the wet or dry coating to be applied to the parts cannot be measured with mechanical contact-type measuring devices. Even if a mechanical contact-type measuring device were used to measure the coated part or parts, the applied coating on the part would be blemished or altered due to the contact of the measuring device on the coating which renders the part or parts unusable.
In other known coating systems, prior to coating the part, the part is measured to determine if it is within acceptable dimensional ranges established for the part. If the part is within the acceptable dimension range, the amount of coating needed to coat the part to achieve the final product size is calculated and then applied to the part. After the coating is applied, the part is measured to ensure that the coated part is still within the dimensional tolerance limits and design specifications for the part. If the coated part is not within the dimensional tolerance limits and/or the design specifications for the part, the part is unusable and either the coating is removed and subsequently re-applied or the part is discarded. If the part falls within the tolerance limits and design specifications for the part, the part is removed from the part support and transported to the manufacturer, purchaser or user of the part.
One known problem with such known coating processes is that the coating that is applied to the part is applied without any measurements taken while the part is being coated. After completion of the coating process, the coated part is measured to determine if it is within established dimensional tolerance levels and design specifications. If the coated part is not within the established tolerance levels and design specifications, the part cannot be used for its intended purpose. If the part is too large or too big, the part dimension cannot be reduced in order to meet the desired design specifications. Similarly, if the part is too small after applying the coating, additional coating cannot be applied because the original coating has been dried or oven cured and additional layers of coating would diminish the strength and durability of the part due to poor adhesion between the coating layers. Specifically, when low friction coatings such as Teflon® are used to coat a surface of a part and the coated surface is cured, the coated surface cannot be re-coated if the measured dimension of the part is too small. As a result, the coating on the part must be completely removed before the part can be re-coated or the part must be discarded. However, even if more coating could be added to the part, this essentially doubles the amount of time spent to produce a dimensionally acceptable part.
Therefore, a significant margin of error is introduced into or present in the known coating processes based on the calculation of the amount of coating to be applied to achieve the final product. The known coating processes calculate the total amount of coating needed to achieve the final part size only at the beginning of the coating process and in certain systems based on measurements taken of a group or lot of parts instead of individually on the part to be coated. In such case, all of the calculated amount of coating is applied to the part. Applying a large amount of coating to the part is less accurate than applying a smaller amount of coating because the margin of error is greater. As a result, some or all of the parts in a lot or batch of parts are unusable because the coated part or parts are outside of the acceptable dimensional tolerance levels for the part or parts.
Accordingly, there is a need for a coating apparatus and method that accurately measures a part size and/or the maximum and minimum coating thicknesses of a part while coating the part so that the part is coated with greater accuracy, consistency and efficiency, to provide complete usability of an entire lot or batch of parts. Additionally, there is a need for a coating apparatus and method that accepts varying uncoated part sizes and selectively applies a proportional amount of coating to the uncoated parts to generate coated parts, which have a final coated size within the desired design specifications for the parts.